DSL EXPRESSION:
$z=max(1,2,3,)

AST:
"block" [tt:block] [nt:StatementBlock]
    "=" [tt:equals] [nt:Assignment]
        "$z" [tt:field_name] [nt:DirectFieldValue]
        "max" [tt:non_sigil_name] [nt:FunctionCallsite]
            "1" [tt:int_literal] [nt:int_literal]
            "2" [tt:int_literal] [nt:int_literal]
            "3" [tt:int_literal] [nt:int_literal]

